arch: Cleanup of __ARM__ checks

* gcc 7.x defines __arm__ and __ARM__ (and others)
* clang defines __arm__ and __arm
* cleanup a few related ifdef vs if macros

Change-Id: I5da4bafac590f6fa3e10e543688001c2449f840d

headers/config/HaikuConfig.h

@@ -18,7 +18,7 @@
    __HAIKU_BIG_ENDIAN			- defined to 1 on big endian architectures
    								  (defaults to undefined)
 */
-#ifdef __INTEL__
+#if defined(__INTEL__)
 #	define __HAIKU_ARCH					x86
 #	if __GNUC__ == 2
 #		define __HAIKU_ARCH_ABI			"x86_gcc2"
@@ -27,31 +27,31 @@
 #	endif
 #	define __HAIKU_ARCH_X86				1
 #	define __HAIKU_ARCH_PHYSICAL_BITS	64
-#elif __x86_64__
+#elif defined(__x86_64__)
 #	define __HAIKU_ARCH					x86_64
 #	define __HAIKU_ARCH_ABI				"x86_64"
 #	define __HAIKU_ARCH_X86_64			1
 #	define __HAIKU_ARCH_BITS			64
-#elif __POWERPC__
+#elif defined(__POWERPC__)
 #	define __HAIKU_ARCH					ppc
 #	define __HAIKU_ARCH_ABI				"ppc"
 #	define __HAIKU_ARCH_PPC				1
 #	define __HAIKU_ARCH_PHYSICAL_BITS	64
 #	define __HAIKU_BIG_ENDIAN			1
-#elif __M68K__
+#elif defined(__M68K__)
 #	define __HAIKU_ARCH					m68k
 #	define __HAIKU_ARCH_ABI				"m68k"
 #	define __HAIKU_ARCH_M68K			1
 #	define __HAIKU_BIG_ENDIAN			1
-#elif __MIPSEL__
+#elif defined(__MIPSEL__)
 #	define __HAIKU_ARCH					mipsel
 #	define __HAIKU_ARCH_ABI				"mipsel"
 #	define __HAIKU_ARCH_MIPSEL			1
-#elif __ARM__ || __ARMEL__
+#elif defined(__ARMEL__) || defined(__arm__)
 #	define __HAIKU_ARCH					arm
 #	define __HAIKU_ARCH_ABI				"arm"
 #	define __HAIKU_ARCH_ARM				1
-#elif __ARMEB__
+#elif defined(__ARMEB__)
 #	define __HAIKU_ARCH					armeb
 #	define __HAIKU_ARCH_ABI				"armeb"
 #	define __HAIKU_ARCH_ARM				1

headers/os/kernel/debugger.h

@@ -20,17 +20,17 @@
 #include <arch/arm/arch_debugger.h>
 
 
-#ifdef __x86_64__
+#if defined(__x86_64__)
 	typedef struct x86_64_debug_cpu_state debug_cpu_state;
-#elif __INTEL__
+#elif defined( __INTEL__)
 	typedef struct x86_debug_cpu_state debug_cpu_state;
-#elif __POWERPC__
+#elif defined(__POWERPC__)
 	typedef struct ppc_debug_cpu_state debug_cpu_state;
-#elif __M68K__
+#elif defined(__M68K__)
 	typedef struct m68k_debug_cpu_state debug_cpu_state;
-#elif __MIPSEL__
+#elif defined(__MIPSEL__)
 	typedef struct mipsel_debug_cpu_state debug_cpu_state;
-#elif __ARM__
+#elif defined(__arm__)
 	typedef struct arm_debug_cpu_state debug_cpu_state;
 #else
 	#error unsupported architecture

headers/posix/arch/arm/signal.h

@@ -10,7 +10,7 @@
  * Architecture-specific structure passed to signal handlers
  */
 
-#if __ARM__
+#if defined(__arm__)
 struct vregs
 {
 	ulong r0;
@@ -32,7 +32,7 @@ struct vregs
 	ulong cpsr;
 // TODO: ARM: fix floats in vregs, add missing stuff.
 };
-#endif /* __ARM__ */
+#endif /* defined(__arm__) */
 
 
 #endif /* _ARCH_SIGNAL_H_ */

headers/posix/fenv.h

@@ -5,7 +5,7 @@
 #  include <arch/x86/fenv.h>
 #elif defined(__x86_64__)
 #  include <arch/x86_64/fenv.h>
-#elif defined(__ARM__)
+#elif defined(__arm__)
 #  include <arch/arm/fenv.h>
 #elif defined(__POWERPC__)
 #  include <arch/ppc/fenv.h>